Sensitivity of Neutron-Rich Nuclear Isomer Behavior to Uncertainties in Direct Transitions

Abstract

Nuclear isomers are populated in the rapid neutron capture process (r process) of nucleosynthesis. The r process may cover a wide range of temperatures, potentially starting from several tens of GK (several MeV) and then cooling as material is ejected from the event. As the r-process environment cools, isomers can freeze out of thermal equilibrium or be directly populated as astrophysical isomers (astromers). Two key behaviors of astromers -- ground state<->isomer transition rates and thermalization temperatures -- are determined by direct transition rates between pairs of nuclear states. We perform a sensitivity study to constrain the effects of unknown transitions on astromer behavior. We also introduce a categorization of astromers that describes their potential effects in hot environments. We provide a table of neutron-rich isomers that includes the astromer type, thermalization temperature, and key unmeasured transition rates.

52 pages, 13 figures, 2 tables

References in corpus (7)

• Measurement of the ${}^{229}$Th isomer energy with a magnetic micro-calorimeter
• Astromers in the radioactive decay of r-process nuclei
• The impact of isomers on a kilonova associated with neutron star mergers
• Novel Penning-trap techniques reveal isomeric states in ${}^{128}$In and ${}^{130}$In for the first time
• Properties of 187Ta revealed through isomeric decay
• New 34Cl proton-threshold states and the thermonuclear 33S(p,gamma)34Cl rate in ONe novae
• The role of excited states in rp-process for sd shell nuclei